Associations of heavy metals and urinary sodium excretion with obesity in adults: A cross-sectional study from Korean Health Examination and Nutritional Survey

Overview

This cross-sectional study uses data from 6,609 Korean adults in KNHANES 2008–2012 to examine associations between biomarkers of heavy metal exposure (serum mercury (Hg), serum cadmium (Cd), urinary As) and overweight/obesity, with a focus on the interactive effect of high sodium excretion and high mercury. The primary finding is that higher serum mercury (≥5.1 µg/L vs. <3.0 µg/L) was significantly associated with overweight/obesity (OR=1.57, 95% CI 1.31–1.88), and this effect was amplified in participants with high urinary sodium excretion (combined OR=3.61 vs. lowest tertiles for both). The study is most relevant to the wiki as a source of population-level biomonitoring data for total mercury (tHg), Cd, and urinary As in a Korean reference population, with exposures principally attributed to fish consumption (Hg) and dietary sources (Cd, As).

Key numbers

Biomarker levels (mean ± SD) by obesity status:

• Serum cadmium (µg/L): overall 1.0 ± 0.7; normal weight 0.8 ± 0.7; overweight/obese 1.1 ± 0.7 (p < 0.01)
• Serum mercury (µg/L): overall 3.8 ± 2.9; normal weight 3.1 ± 2.0; overweight/obese 4.5 ± 3.7 (p < 0.01)
• Urinary arsenic excretion (µg/L): overall 111.7 ± 122.5; not significantly associated with obesity (p = 0.14)

Analytical methods:

• Serum Cd: AAS (AAnalyst 600, PerkinElmer); LOD 0.081 µg/L
• Serum Hg: Gold amalgamation technique (DMA-80, Milestone); LOD 0.05 µg/L
• Urinary arsenic (As): Graphite furnace AAS (AAnalyst 600, PerkinElmer); LOD 1.679 mg/L (note: unusually high LOD for urinary As; likely reflects total urinary As including organic seafood arsenicals, not speciated iAs)

Obesity risk associations (polytomous logistic regression, reference = normal weight):

• Serum Hg ≥5.1 µg/L vs. <3.0 µg/L: OR = 1.57 (95% CI 1.31–1.88) for overweight/obesity
• Urinary sodium ≥3588.8 mg/day vs. <2885.6 mg/day: OR = 2.21 (95% CI 1.84–2.66)
• Combined high Hg + high sodium (3T/3T vs. 1T/1T): OR = 3.61 (95% CI 2.61–5.00)
• Serum Cd and urinary As: not significantly associated with overweight/obesity

CDC/EPA safety threshold exceedances (~7% of participants, n=472): serum Cd >5 µg/L, serum Hg >10 µg/L, or urine As >35 µg/g creatinine.

Methods

Cross-sectional study; Korea National Health and Nutrition Examination Survey (KNHANES) 2008–2012; stratified multistage probability sampling; n=12,000 initial; 6,609 after excluding cancer/CVD/chronic kidney/liver disease and missing data. Serum Cd by AAS; serum Hg by gold amalgamation; urinary As by GFAAS. Heavy metals measured at Neodin Medical Research Institute. Polytomous logistic regression adjusted for age, sex, smoking, alcohol, physical activity, diet (energy and potassium intake), education, marital status, hypertension, diabetes. Note: urinary As LOD of 1.679 mg/L is very high and suggests total As (including organic seafood arsenicals); inorganic speciation not performed. Serum Hg without speciation is reported as total Hg; in the Korean population with high seafood consumption, organic methylmercury is the predominant species.

Implications

Certification: Provides biomonitoring reference values for tHg (mean 3.8 µg/L serum), Cd (mean 1.0 µg/L), and urinary As in a large Korean adult cohort. Korean populations have well-documented high dietary fish/seafood exposure driving elevated Hg biomarkers; these values are context for understanding exposure levels in high-fish-consumption populations. Not directly applicable to product concentration limits, but relevant for health outcome context pages.

Courses: Illustrates the range of real-world human exposure to Hg, Cd, and As via diet in a large national survey. The mercury-obesity association (if causal) would represent an adverse health outcome beyond classical neurotoxicity. The interactive mercury-sodium effect, if replicated, has implications for populations combining high seafood consumption with high-sodium diets.

App: The urinary As data are difficult to interpret for food safety (LOD too high; no speciation) but the serum Hg distribution is a useful population reference. Not directly applicable to ingredient-list risk scoring.

Related evidence

• Mercury
• Cadmium
• health/biomonitoring-reference-values

Update history

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